609.006 rounded to hundredths is 609.01 because the thousandths place
was 6, which is 5 or more, so we increase the 0 in the hundredths place
by 1, and drop the 6 in the thousandths place.

However, if your problem had been 609.004, then when rounded to hundredths
it would be 609.00 because the thousandths place was 4, which is less than
5, so we leave the 0 in the hundredths place as 0, and drop the 4 in the
thousandths place.

Edwin